DPDK patches and discussions
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From: Ray Kinsella <mdr@ashroe.eu>
To: David Marchand <david.marchand@redhat.com>
Cc: Thomas Monjalon <thomas@monjalon.net>,
	Neil Horman <nhorman@tuxdriver.com>,
	Luca Boccassi <bluca@debian.org>,
	Kevin Traynor <ktraynor@redhat.com>,
	"Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
	Akhil Goyal <akhil.goyal@nxp.com>,
	"Trahe, Fiona" <fiona.trahe@intel.com>,
	Ferruh Yigit <ferruh.yigit@intel.com>, dev <dev@dpdk.org>,
	Anoob Joseph <anoobj@marvell.com>,
	"Kusztal, ArkadiuszX" <arkadiuszx.kusztal@intel.com>,
	"Richardson, Bruce" <bruce.richardson@intel.com>,
	"Mcnamara, John" <john.mcnamara@intel.com>,
	dodji@seketeli.net, Andrew Rybchenko <arybchenko@solarflare.com>,
	Aaron Conole <aconole@redhat.com>
Subject: Re: [dpdk-dev] [PATCH v2 4/4] add ABI checks
Date: Wed, 5 Feb 2020 11:10:02 +0000
Message-ID: <38175d6a-09a3-60a9-d920-785d9ef17c41@ashroe.eu> (raw)
In-Reply-To: <CAJFAV8xg55tbhPSB4Xnkb7X862KChJSsgUZWmDJsUk71gvMptg@mail.gmail.com>



On 04/02/2020 09:51, David Marchand wrote:
> On Mon, Feb 3, 2020 at 7:56 PM Ray Kinsella <mdr@ashroe.eu> wrote:
>> On 03/02/2020 17:34, Thomas Monjalon wrote:
>>> 03/02/2020 18:09, Thomas Monjalon:
>>>> 03/02/2020 10:30, Ferruh Yigit:
>>>>> On 2/2/2020 2:41 PM, Ananyev, Konstantin wrote:
>>>>>> 02/02/2020 14:05, Thomas Monjalon:
>>>>>>> 31/01/2020 15:16, Trahe, Fiona:
>>>>>>>> On 1/30/2020 8:18 PM, Thomas Monjalon wrote:
>>>>>>>>> If library give higher value than expected by the application,
>>>>>>>>> if the application uses this value as array index,
>>>>>>>>> there can be an access out of bounds.
>>>>>>>>
>>>>>>>> [Fiona] All asymmetric APIs are experimental so above shouldn't be a problem.
>>>>>>>> But for the same issue with sym crypto below, I believe Ferruh's explanation makes
>>>>>>>> sense and I don't see how there can be an API breakage.
>>>>>>>> So if an application hasn't compiled against the new lib it will be still using the old value
>>>>>>>> which will be within bounds. If it's picking up the higher new value from the lib it must
>>>>>>>> have been compiled against the lib so shouldn't have problems.
>>>>>>>
>>>>>>> You say there is no ABI issue because the application will be re-compiled
>>>>>>> for the updated library. Indeed, compilation fixes compatibility issues.
>>>>>>> But this is not relevant for ABI compatibility.
>>>>>>> ABI compatibility means we can upgrade the library without recompiling
>>>>>>> the application and it must work.
>>>>>>> You think it is a false positive because you assume the application
>>>>>>> "picks" the new value. I think you miss the case where the new value
>>>>>>> is returned by a function in the upgraded library.
>>>>>>>
>>>>>>>> There are also no structs on the API which contain arrays using this
>>>>>>>> for sizing, so I don't see an opportunity for an appl to have a
>>>>>>>> mismatch in memory addresses.
>>>>>>>
>>>>>>> Let me demonstrate where the API may "use" the new value
>>>>>>> RTE_CRYPTO_AEAD_CHACHA20_POLY1305 and how it impacts the application.
>>>>>>>
>>>>>>> Once upon a time a DPDK application counting the number of devices
>>>>>>> supporting each AEAD algo (in order to find the best supported algo).
>>>>>>> It is done in an array indexed by algo id:
>>>>>>> int aead_dev_count[RTE_CRYPTO_AEAD_LIST_END];
>>>>>>> The application is compiled with DPDK 19.11,
>>>>>>> where RTE_CRYPTO_AEAD_LIST_END = 3.
>>>>>>> So the size of the application array aead_dev_count is 3.
>>>>>>> This binary is run with DPDK 20.02,
>>>>>>> where RTE_CRYPTO_AEAD_CHACHA20_POLY1305 = 3.
>>>>>>> When calling rte_cryptodev_info_get() on a device QAT_GEN3,
>>>>>>> rte_cryptodev_info.capabilities.sym.aead.algo is set to
>>>>>>> RTE_CRYPTO_AEAD_CHACHA20_POLY1305 (= 3).
>>>>>>> The application uses this value:
>>>>>>> ++ aead_dev_count[info.capabilities.sym.aead.algo];
>>>>>>> The application is crashing because of out of bound access.
>>>>>>
>>>>>> I'd say this is an example of bad written app.
>>>>>> It probably should check that returned by library value doesn't
>>>>>> exceed its internal array size.
>>>>>
>>>>> +1
>>>>>
>>>>> Application should ignore values >= MAX.
>>>>
>>>> Of course, blaming the API user is a lot easier than looking at the API.
>>>> Here the API has RTE_CRYPTO_AEAD_LIST_END which can be understood
>>>> as the max value for the application.
>>>> Value ranges are part of the ABI compatibility contract.
>>>> It seems you expect the application developer to be aware that
>>>> DPDK could return a higher value, so the application should
>>>> check every enum values after calling an API. CRAZY.
>>>>
>>>> When we decide to announce an ABI compatibility and do some marketing,
>>>> everyone is OK. But when we need to really make our ABI compatible,
>>>> I see little or no effort. DISAPPOINTING.
>>>>
>>>>> Do you suggest we don't extend any enum or define between ABI breakage releases
>>>>> to be sure bad written applications not affected?
>>>>
>>>> I suggest we must consider not breaking any assumption made on the API.
>>>> Here we are breaking the enum range because nothing mentions _LIST_END
>>>> is not really the absolute end of the enum.
>>>> The solution is to make the change below in 20.02 + backport in 19.11.1:
>>>
>>> Thinking twice, merging such change before 20.11 is breaking the
>>> ABI assumption based on the API 19.11.0.
>>> I ask the release maintainers (Luca, Kevin, David and me) and
>>> the ABI maintainers (Neil and Ray) to vote for a or b solution:
>>>       a) add comment and LIST_MAX as below in 20.02 + 19.11.1
>>
>> That would still be an ABI breakage though right.
> 
> Yes.
> 
> 
>>
>>>       b) wait 20.11 and revert Chacha-Poly from 20.02
>>
>> Thanks for analysis above Fiona, Ferruh and all.
>>
>> That is a nasty one alright - there is no "good" answer here.
>> I agree with Ferruh's sentiments overall, we should rethink this API for 20.11.
>> Could do without an enumeration?
>>
>> There a c) though right.
>> We could work around the issue by api versioning rte_cryptodev_info_get() and friends.
> 
> It has a lot of friends, but it sounds like the right approach.

+1

> Is someone looking into this?

Looks to be in hand now.

> 
> 
>> So they only support/acknowledge the existence of Chacha-Poly for applications build against > 20.02.
>>
>> It would be painful I know.
>> It would also mean that Chacha-Poly would only be available to those building against >= 20.02.
> 
> Yes.
> 
> 
> --
> David Marchand
> 

  parent reply index

Thread overview: 104+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-20 15:20 [dpdk-dev] [PATCH] " David Marchand
2019-12-20 15:32 ` Richardson, Bruce
2019-12-20 16:20   ` Kinsella, Ray
2019-12-20 21:00     ` Thomas Monjalon
2020-01-06 13:17       ` Aaron Conole
2020-01-15 13:07         ` Burakov, Anatoly
2020-01-14 23:19     ` Thomas Monjalon
2020-01-15 11:33       ` Neil Horman
2020-01-15 12:38         ` Thomas Monjalon
2020-01-16 11:52           ` Neil Horman
2020-01-16 14:20             ` Thomas Monjalon
2020-01-16 18:49               ` Neil Horman
2020-01-16 20:01                 ` Thomas Monjalon
2020-01-17 19:01                   ` Neil Horman
2020-01-17 21:26                     ` David Marchand
2019-12-20 20:25 ` Neil Horman
2020-01-29 17:26 ` [dpdk-dev] [PATCH v2 0/4] " David Marchand
2020-01-29 17:26   ` [dpdk-dev] [PATCH v2 1/4] hash: fix meson headers packaging David Marchand
2020-01-30 10:12     ` Luca Boccassi
2020-01-30 10:54       ` David Marchand
2020-01-30 10:56         ` Luca Boccassi
2020-01-29 17:26   ` [dpdk-dev] [PATCH v2 2/4] build: split build helper David Marchand
2020-01-29 17:26   ` [dpdk-dev] [PATCH v2 3/4] build: test meson installation David Marchand
2020-01-29 17:26   ` [dpdk-dev] [PATCH v2 4/4] add ABI checks David Marchand
2020-01-29 17:42     ` Thomas Monjalon
2020-01-29 18:10       ` Anoob Joseph
2020-01-29 20:03         ` David Marchand
2020-01-29 20:13           ` Akhil Goyal
2020-01-30 16:09             ` Ferruh Yigit
2020-01-30 20:18               ` Thomas Monjalon
2020-01-31  9:03                 ` Ferruh Yigit
2020-01-31 10:26                   ` Ananyev, Konstantin
2020-01-31 14:16                 ` Trahe, Fiona
2020-02-02 13:05                   ` Thomas Monjalon
2020-02-02 14:41                     ` Ananyev, Konstantin
2020-02-03  9:30                       ` Ferruh Yigit
2020-02-03 11:50                         ` Neil Horman
2020-02-03 13:09                           ` Ferruh Yigit
2020-02-03 14:00                             ` Dodji Seketeli
2020-02-03 14:46                               ` Ferruh Yigit
2020-02-03 15:08                             ` Trahe, Fiona
2020-02-03 17:09                         ` Thomas Monjalon
2020-02-03 17:34                           ` Thomas Monjalon
2020-02-03 18:55                             ` Ray Kinsella
2020-02-03 21:07                               ` Thomas Monjalon
2020-02-04  9:46                                 ` Ferruh Yigit
2020-02-04 10:24                                 ` Thomas Monjalon
2020-02-04 12:44                                   ` Trahe, Fiona
2020-02-04 15:52                                     ` Trahe, Fiona
2020-02-04 15:59                                       ` Thomas Monjalon
2020-02-04 17:46                                         ` Trahe, Fiona
2020-02-13 14:51                                           ` Kusztal, ArkadiuszX
2020-03-16 12:57                                             ` Trahe, Fiona
2020-03-16 13:09                                               ` Thomas Monjalon
2020-03-17 13:27                                                 ` Kusztal, ArkadiuszX
2020-03-17 15:10                                                   ` Thomas Monjalon
2020-03-17 19:10                                                     ` Kusztal, ArkadiuszX
2020-02-04 12:57                                   ` Kevin Traynor
2020-02-04 14:44                                   ` Aaron Conole
2020-02-04 19:49                                     ` Neil Horman
2020-02-04  9:51                               ` David Marchand
2020-02-04 10:10                                 ` Trahe, Fiona
2020-02-04 10:38                                   ` Thomas Monjalon
2020-02-05 11:10                                 ` Ray Kinsella [this message]
2020-02-03 17:40                           ` Ferruh Yigit
2020-02-03 18:40                             ` Thomas Monjalon
2020-02-04  9:19                               ` Ferruh Yigit
2020-02-04  9:45                                 ` Thomas Monjalon
2020-02-04  9:56                                   ` Ferruh Yigit
2020-02-04 10:08                                     ` Bruce Richardson
2020-02-04 10:17                                     ` Kevin Traynor
2020-02-04 10:16                             ` Akhil Goyal
2020-02-04 10:28                               ` Thomas Monjalon
2020-02-04 10:32                                 ` Akhil Goyal
2020-02-04 11:35                                   ` Bruce Richardson
2020-02-04 22:10                                   ` Neil Horman
2020-02-05  6:16                                     ` [dpdk-dev] [EXT] " Anoob Joseph
2020-02-05 14:33                                       ` Trahe, Fiona
2020-02-04 21:59                               ` [dpdk-dev] " Neil Horman
2020-01-30 13:06         ` Trahe, Fiona
2020-01-30 15:59           ` Thomas Monjalon
2020-01-30 16:42             ` Ferruh Yigit
2020-01-30 23:49             ` Ananyev, Konstantin
2020-01-31  9:07               ` Ferruh Yigit
2020-01-31  9:37                 ` Ananyev, Konstantin
2020-01-30 10:57   ` [dpdk-dev] [PATCH v2 0/4] " Luca Boccassi
2020-01-30 16:00 ` [dpdk-dev] [PATCH v3 " David Marchand
2020-01-30 16:00   ` [dpdk-dev] [PATCH v3 1/4] hash: fix meson headers packaging David Marchand
2020-01-30 18:01     ` Wang, Yipeng1
2020-01-30 18:40       ` Honnappa Nagarahalli
2020-02-05 19:51         ` Wang, Yipeng1
2020-01-30 16:00   ` [dpdk-dev] [PATCH v3 2/4] build: split build helper David Marchand
2020-01-30 16:00   ` [dpdk-dev] [PATCH v3 3/4] build: test meson installation David Marchand
2020-01-30 22:17     ` Thomas Monjalon
2020-01-30 16:00   ` [dpdk-dev] [PATCH v3 4/4] add ABI checks David Marchand
2020-01-30 22:32     ` Thomas Monjalon
2020-02-01 15:29       ` David Marchand
2020-01-30 22:44     ` Thomas Monjalon
2020-02-02 21:08 ` [dpdk-dev] [PATCH v4 0/3] " David Marchand
2020-02-02 21:08   ` [dpdk-dev] [PATCH v4 1/3] hash: fix meson headers packaging David Marchand
2020-02-05 19:53     ` Wang, Yipeng1
2020-02-02 21:08   ` [dpdk-dev] [PATCH v4 2/3] build: split build helper David Marchand
2020-02-02 21:08   ` [dpdk-dev] [PATCH v4 3/3] add ABI checks David Marchand
2020-02-05 14:13   ` [dpdk-dev] [PATCH v4 0/3] " Thomas Monjalon

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